APA (7th ed.) Citation

Ennis, C. W., English, J. R., Jansson, D. G., & Samson, C. H. (1990). Improved problem formulation in engineering systems design.

Chicago Style (17th ed.) Citation

Ennis, Charles Walter, John R. English, David G. Jansson, and Charles H. Samson. Improved Problem Formulation in Engineering Systems Design. 1990.

MLA (9th ed.) Citation

Ennis, Charles Walter, et al. Improved Problem Formulation in Engineering Systems Design. 1990.